Automotive radar products are typically made by assembling a number of discrete components on one or more printed circuit boards. Thus, automotive radar products are typically undesirably bulky. Moreover, existing automotive radar products tend to suffer from self-interference between a transmit signal and a receive signal of the radar device. To reduce the self-interference, radar product designs often incorporate several techniques that tend to increase the size and cost of the product. For example, the discrete components, or groups of discrete components, are somewhat isolated from each other by distance and/or other radio frequency (RF) isolation barriers configured to reduce the self-interference.
In traditional radar embodiments, and with reference to FIG. 1A, a transmitter and a receiver are made up of discrete components. Single signal lines connect the individual components to each other and a digital signal processor (DSP) module 110. Moreover, assembling discrete components results in an overall size increase in comparison to highly integrated circuit architecture.
Additionally, current narrowband frequency modulated continuous wave (FMCW) automotive radar products transmit a signal with a frequency ramp in discrete frequency steps. The discrete frequency steps are created using a digital-to-analog converter (DAC) integrated circuit 154 to tune a free-running voltage controlled oscillator (VCO) 101. With reference to FIG. 1B, the VCO 101 is typically built with a discrete GaAs FET and a discrete varactor diode. The DAC 154 is typically located on DSP module 110 and an analog tuning voltage control signal is communicated from the DSP module to an RF module 105 containing VCO 101. However, traversing a board-to-board connection makes the analog tuning voltage control signal more susceptible to noise. The source of tuning noise may be a PWM 152, DAC 154, an adder or summing circuit, or interface induced noise.
In this typical architecture of a board-to-board connection, DAC 154 is placed in close proximity to VCO 101 to limit noise coupling with the output of DAC 154. However, the proximity of DAC 154 to VCO 101 should also be limited due to digital noise from the DAC programming lines. The balancing of these two limitations commonly results in isolation of VCO 101 from DAC 154 using metal compartments, again causing the system to be larger and more costly.
Typically, making an automotive radar product smaller has the result of worsening the isolation between transmit and receive signals. Nevertheless, a need exists for a more compact radar embodiment having improved isolation of transmit and receive signals. This invention addresses these needs and others.